. 2017 Apr 29;7(5):51.

doi: 10.3390/brainsci7050051.

In Search of Sleep Biomarkers of Alzheimer's Disease: K-Complexes Do Not Discriminate between Patients with Mild Cognitive Impairment and Healthy Controls

Affiliations

¹ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. flaminia.reda@uniroma1.it.
² Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. maurizio.gorgoni@uniroma1.it.
³ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. giulia.lauri@uniroma1.it.
⁴ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. ilaria.truglia@uniroma1.it.
⁵ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. susanna.cordone@uniroma1.it.
⁶ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. serena.scarpelli@uniroma1.it.
⁷ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. anastasia.mangiaruga@uniroma1.it.
⁸ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. aurora.datri@uniroma1.it.
⁹ Department of Biotechnological and Applied Clinical Science, University of L'Aquila, L'Aquila 67100, Italy. michele.ferrara@univaq.it.
¹⁰ Institute of Neurology, Catholic University of The Sacred Heart, Rome 00168, Italy. g.lacidogna@libero.it.
¹¹ Institute of Neurology, Catholic University of The Sacred Heart, Rome 00168, Italy. camillo.marra@policlinicogemelli.it.
¹² Institute of Neurology, Catholic University of The Sacred Heart, Rome 00168, Italy. paolomaria.rossini@policlinicogemelli.it.
¹³ Istituto di Ricovero e Cura a Carattere Scientifico, San Raffaele Pisana, Rome 00163, Italy. paolomaria.rossini@policlinicogemelli.it.
¹⁴ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. luigi.degennaro@uniroma1.it.

PMID: 28468235
PMCID: PMC5447933
DOI: 10.3390/brainsci7050051

In Search of Sleep Biomarkers of Alzheimer's Disease: K-Complexes Do Not Discriminate between Patients with Mild Cognitive Impairment and Healthy Controls

Flaminia Reda et al. Brain Sci. 2017.

. 2017 Apr 29;7(5):51.

doi: 10.3390/brainsci7050051.

Authors

Affiliations

¹ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. flaminia.reda@uniroma1.it.
² Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. maurizio.gorgoni@uniroma1.it.
³ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. giulia.lauri@uniroma1.it.
⁴ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. ilaria.truglia@uniroma1.it.
⁵ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. susanna.cordone@uniroma1.it.
⁶ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. serena.scarpelli@uniroma1.it.
⁷ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. anastasia.mangiaruga@uniroma1.it.
⁸ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. aurora.datri@uniroma1.it.
⁹ Department of Biotechnological and Applied Clinical Science, University of L'Aquila, L'Aquila 67100, Italy. michele.ferrara@univaq.it.
¹⁰ Institute of Neurology, Catholic University of The Sacred Heart, Rome 00168, Italy. g.lacidogna@libero.it.
¹¹ Institute of Neurology, Catholic University of The Sacred Heart, Rome 00168, Italy. camillo.marra@policlinicogemelli.it.
¹² Institute of Neurology, Catholic University of The Sacred Heart, Rome 00168, Italy. paolomaria.rossini@policlinicogemelli.it.
¹³ Istituto di Ricovero e Cura a Carattere Scientifico, San Raffaele Pisana, Rome 00163, Italy. paolomaria.rossini@policlinicogemelli.it.
¹⁴ Department of Psychology, Sapienza University of Rome, Rome 00185, Italy. luigi.degennaro@uniroma1.it.

PMID: 28468235
PMCID: PMC5447933
DOI: 10.3390/brainsci7050051

Abstract

The K-complex (KC) is one of the hallmarks of Non-Rapid Eye Movement (NREM) sleep. Recent observations point to a drastic decrease of spontaneous KCs in Alzheimer's disease (AD). However, no study has investigated when, in the development of AD, this phenomenon starts. The assessment of KC density in mild cognitive impairment (MCI), a clinical condition considered a possible transitional stage between normal cognitive function and probable AD, is still lacking. The aim of the present study was to compare KC density in AD/MCI patients and healthy controls (HCs), also assessing the relationship between KC density and cognitive decline. Twenty amnesic MCI patients underwent a polysomnographic recording of a nocturnal sleep. Their data were compared to those of previously recorded 20 HCs and 20 AD patients. KCs during stage 2 NREM sleep were visually identified and KC densities of the three groups were compared. AD patients showed a significant KC density decrease compared with MCI patients and HCs, while no differences were observed between MCI patients and HCs. KC density was positively correlated with Mini-Mental State Examination (MMSE) scores. Our results point to the existence of an alteration of KC density only in a full-blown phase of AD, which was not observable in the early stage of the pathology (MCI), but linked with cognitive deterioration.

Keywords: Alzheimer’s disease; EEG; K-complexes; amnesic mild cognitive impairment; cognitive decline; sleep.

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Conflict of interest statement

The authors declare that there is no conflict of interest regarding the publication of this paper. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

Figures

**Figure 1**
K-Complex (KC) density of Alzheimer’s disease (AD) patients (black bar), mild cognitive impairment (MCI) patients (grey bar) and healthy controls (HCs) (white bar) at Fz cortical derivation. Error bars represent the standard errors. Asterisks (*) indicate statistically significant differences (p ≤ 0.05) between groups after post hoc unpaired t-tests.

**Figure 2**
Scatterplot of the individual correlations between Mini Mental State Evaluation (MMSE) scores and K-Complex (KC) density at Fz cortical derivation (p ≤ 0.05). Pearson’s r and relative p value are reported.

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In Search of Sleep Biomarkers of Alzheimer's Disease: K-Complexes Do Not Discriminate between Patients with Mild Cognitive Impairment and Healthy Controls

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In Search of Sleep Biomarkers of Alzheimer's Disease: K-Complexes Do Not Discriminate between Patients with Mild Cognitive Impairment and Healthy Controls

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